The present invention relates generally to pharmaceutical compounds and methods for medical treatment, and more particularly to the composition, synthesis, formulation and use of certain derivatives of the amino acid taurine, for the treatment of ophthalmic disorders.
The retina is a layer of cells which form the inside lining of the back of the mammalian eye. The retina includes certain specialized photoreceptor cells which convert light energy into electrical impulses. These specialized photoreceptor cells of the retina include xe2x80x9crodsxe2x80x9d which emit impulses corresponding to black and white images and xe2x80x9cconesxe2x80x9d which emit impulses corresponding to colored images.
A number of diseases and disorders of the retina are characterized or caused by degeneration of the retinal tissue. Examples of these degenerative retinopathies include: retinitis pigmentosa, macular degeneration and diabetic retinopathy. The available medical and surgical treatments for these degenerative retinopathies have been less than perfect, and many patients continue to suffer full or partial losses of vision due to these disorders.
Relatively high concentrations of the amino acid taurine have been identified in the outer segments of retinal photoreceptor cells, and it has been determined that taurine may be released from the retina in response to light stimulation. It has been further determined that high levels af taurine in the retina may protects the outer segments of the photoreceptor cells from light-induced structural damage. A postulated mechanism for this photo-protective effect is that certain taurine derivatives (e.g, metabolites or break-down products which are formed by the retina""s natural action on the taurine compound) may facilitate the transport of certain photoprotective compounds related to Vitamin Axe2x80x94known as retinoidsxe2x80x94between the pigment epithelium and the photoreceptor cells. In particular, applicant""s research has identified a particular taurine derivative known as retinyliden tauret which is naturally present in the retina and pigment epithelium, and which has exhibited some photoprotective effects in in vitro experiments performed on frog retinas. It is postulated that cis and trans isomers of retinyliden tauret may facilitate the transport of retinoids, in opposite directions, through microscopic channels in the outer segments of the retina""s photoreceptor cells. Tauret: Further Studies of the Role of Taurine in Retina; Petrosian, A. M, Functional Neurochemistry and Cardiology, pp. 471-475 (Wiley-Liss, 1990)
Given the experimentally demonstrated potential for retinyliden tauret to affect light-induced damage to the retina, it is desirable to devise methods for synthesizing retinyliden tauret in substantial quantities, and to develop therapeutic methods for the administration of exogenous retinyliden tauret to the retina of a human or other mammal to deter or treat degenerative retinopathies or to protect the retina from damage.
The present invention provides methods for treating or protecting the retina of a mammalian eye or other tissues by contacting with the retinal or other tissue a therapeutically effective amount of a water soluble derivative of taurine and retinoic acid. Suck compound my comprise retinyliden tauret, which facilitates the transport of at least one retinoid between the pigment epithelium and the photoreceptor cells of the epithelium.
Further in accordance with the present invention, there are provided methods for synthesizing all-trans-[3,7-dimethyl-9-(2,6,6-trimehyl-1-cyclohexen-1-yl)-2,4,6,8-nonatetraen-1-imido-(N-ethane sulfonic acid)] and 11-cis-[3,7-dimethyl-9-(2,6,6-trimehyl-1-cyclohexen-1-yl)-2,4,6,8-nonatetraen-1-imido-(N-ethane sulfonic acid)], as well as formulations and methods for administering such compounds to the retina of a mammalian eye to treat or protect the retina.
Further aspects and advantages of the invention will become apparent to persons of skill in the art upon reading and understanding of the detailed descriptions of preferred embodiments set forth herebelow.